Sampling-Time Harmonic Calculation of Cascaded H-Bridge Converter Based on Phase-Shifted Carrier Pulsewidth Modulation

Harmonics have always been a problem to be solved in converter applications. Studying the source of harmonics and accurately predicting their content has also become one of the research directions. In this paper, the effect of sampling on the output harmonics in the actual system is fully considered. The cascaded H-bridge model based on phase-shifted carrier pulsewidth modulation (PSC-PWM) is modified by theoretical analysis and the accurate harmonic expression is obtained by applying the double-Fourier transform. The amplitude and phase of each harmonic can be accurately calculated and its presence can be better explained, which has great significance for eliminating specific harmonics and improving power quality. The correctness of the calculation is proved by simulation and experimental results.